The present invention relates generally to a method for improving the accuracy of data obtained in a diagnostic medical imaging apparatus that employs a near-infrared laser as a radiation source and a detector array with variable gain amplifiers that can accommodate the wide dynamic range of signals available from each detectors.
It is an object of the present invention to provide a method for collecting data for use in image reconstruction of an object being scanned using an optical tomographic scanner where the method accommodates the large dynamic range of light levels that can vary as high as 107:1.
It is another object of the present invention to provide a method for collecting data for use in image reconstruction of an object being scanned that provides for reducing the error when digitizing the signals generated by photodetectors in an optical tomographic scanner where the signals can range approximately 1 mV-10 V.
In summary, the present invention provides a method for collecting data for use in image reconstruction of an object being scanned, comprising providing a plurality of detectors disposed in an arc around the object being scanned to detect light passing through the object; impinging a laser beam at a point on the object; integrating the output of each detector at a number of successive time intervals, each time interval being longer than the previous time interval; digitizing the integrated output from each time interval; successively digitizing multiple times the integrated output from the longest time interval and averaging the results; orbiting the detectors and laser beam to another point on a circle; and repeating the above steps until a complete circle has been traversed.
The present invention also provides a method for obtaining data from a photodetector array used in image reconstruction where the light intensity impinging on the detectors has a large dynamic range, comprising integrating the output of each photodector in the array for at least two time intervals, each time interval being longer than the previous time interval; digitizing the integrated output of each detector; successively digitizing multiple times the integrated output of each detector at the longest time interval and averaging the results; and selecting the value of the digitized data from the longest time interval for those detectors that did not saturate.
These and other objectives of the present invention will become apparent from the following detailed description.